The runic corpus is one of inscriptions rather than a proven divinatory deck. In the modern revival Isa is commonly read for stillness, standstill, stasis and a freezing of circumstances that calls for patience. This keyword reading belongs to the twentieth-century reconstructionist and esoteric revival, popularized in the 1980s, and is offered here as a symbolic tradition rather than an ancient or predictive practice.
All three surviving rune poems describe ice in essentially physical, descriptive terms, cold, bright, treacherous underfoot, without the moralising or instructive turn several other stanzas take, and the modern divinatory tradition's keyword sense of stillness, standstill and a pause in motion follows this physical description fairly directly rather than requiring reinterpretation of a difficult or divided older source. As with the runes generally, using Isa as an oracular sign for a specific querent's situation is a twentieth-century practice rather than an attested ancient one.
The Armanen-descended rune-magic tradition transmitted into English chiefly through Thorsson's work also treats Isa as usable actively rather than only read passively: chanted aloud as galdr, or carved into wood, metal or a bind-rune combining several staves, for an intended practical effect. No source earlier than the twentieth century attests any such active magical use of this specific rune, and the practice should be understood as a modern reconstruction built on the reconstructed name and the rune poems rather than as a recovered ancient technique.